Voltage value at outlet / isolation transformer

[Foggie]

I have a pretty basic Belkin “line conditioner” (pf60) and it reads 123 or 124v on its meter at idle.  I only have my Preamp, DAC and a LPS (for OpticalRendu) plugged in.

 

I have an isolation transformer (new TrippLite 1000HG) and was going to test it out on the front-end gear for kicks.  I plugged the Belkin into the iso transformer (none of the components were powered on) and the Belkin read 127v?  That seems a bit high and is that normal for an iso transformer to increase the voltage?  The only “load” was the Belkin and I didn’t power on any of the components.

 

I was also going to plug the components directly into the iso transformer, but wanted to understand this a bit more before I do.  Is there an agreed upon voltage range one should have at the outlet (US/120v) and what's either too high or too low?  From a few short snippets I read, there is about a 5-10% (+/-) range that is acceptable?  

 

When you should be concerned about premature wear or damaging gear if voltage is too low or too high if that's a "thing?  I’m assuming any variance will be very dependent on your location/state etc..

 

[Foggie]

I also noticed that the Belkin indicates wiring + ground fault when plugged into iso transformer?  Maybe that's as designed (floating secondary or whatever)?  The meter pick is a stock photo

 

[sandyk]

4 hours ago, Foggie said:

Is there an agreed upon voltage range one should have at the outlet (US/120v) and what's either too high or too low?  From a few short snippets I read, there is about a 5-10% (+/-) range that is acceptable?  

From Wikipaedia 

". . . .In the United States and Canada, national standards specify that the nominal voltage at the source should be 120 V and allow a range of 114 V to 126 V (RMS) (−5% to +5%). Historically 110 V, 115 V and 117 V have been used at different times and places in North America." 

 I would briefly power on one of the components and see if the voltage drops down a little from the iso transformer under load. Most transformers output voltage are a little high without a load.

 All properly designed components will not be bothered by such a small voltage increase, and are designed to tolerate much higher short term voltage variations .

[Speedskater]

NEC and UL now spec 125V as the nominal unloaded line voltage. So don't be surprised if you see an occasional reading in the high one twenty voltage range. This can be a problem for legacy and boutique components that were designed for the 110 to 115V era.  Much of what is called the "DC" problem is in fact over-voltage of the power transformer.

[Foggie]

Just now, sandyk said:

From Wikipaedia 

". . . .In the United States and Canada, national standards specify that the nominal voltage at the source should be 120 V and allow a range of 114 V to 126 V (RMS) (−5% to +5%). Historically 110 V, 115 V and 117 V have been used at different times and places in North America." 

 I would briefly power on one of the components and see if the voltage drops down a little from the iso transformer under load. Most transformers output voltage are a little high without a load.

 All properly designed components will not be bothered by such a small voltage increase, and are designed to tolerate much higher short term voltage variations .

Thanks. So my findings of 5-10% variance appears to be "normal". 

 

I rarely look at the meter (Belkin).  Sitting down now for tunes and just looked at the meter (no iso) and says 125v.  AC is running and prob a busy time in the neighborhood.  I was only using the Belkin into the iso for a meter reading / curiosity and thus my questions. 

 

There are a lot of knowledgeable power individuals here so its nice to pose questions here, hoping some are interested/engaged in this topic.  I don't know what "small voltage increases" are with respect to the engineering side of things / components.  I have what would appear to be very solid engineered components and really just trying to learn a bit on this topic.

 

I suppose what's at my outlet is what it is (not much I can do about it unless its really out of whack) and have been using my current setup for the last 1-2 yrs without issue.   I think my concern was what's too high (or low) and obviously don't want to prematurely wear down components if there is an issue I need to address.   I'll try a few things with the iso

 

 

 

[sandyk]

30 minutes ago, Speedskater said:

NEC and UL now spec 125V as the nominal unloaded line voltage. So don't be surprised if you see an occasional reading in the high one twenty voltage range. This can be a problem for legacy and boutique components that were designed for the 110 to 115V era.  Much of what is called the "DC" problem is in fact over-voltage of the power transformer.

I wonder how something like the attached would go in such a situation, as the overvoltage is quite small. 

 A DIY person could easily find a way to insert one of these (or similar, depending on the power  rating of the iso transformer) in series with the A.C. input to the iso transformer  

 

https://docs.rs-online.com/f3d7/0900766b81580d82.pdf

[Speedskater]

12 hours ago, sandyk said:

I wonder how something like the attached would go in such a situation, as the over-voltage is quite small.

No Thermistors are used to limit inrush current at turn-on. Once they warm-up their resistance drops to a low value.

[sandyk]

9 hours ago, Speedskater said:

No Thermistors are used to limit inrush current at turn-on. Once they warm-up their resistance drops to a low value.

I am well aware of that , which is why I showed the specifications. I was suggesting that a small amount of series resistance in the Primary side may result in a slightly lower voltage output .

For example, at a 1A load, the resistance under load would be 1,471 mOhm (approx) 

In this case we only needed to drop 1 volt . The 10 ohm version may have been more suitable, but that would depend on the power capabilities of the iso transformer and it's actual loading.

Anyway, just a passing thought .